Spunbonded sheets of flash-spun polyolefin plexifilamentary film-fibril strands have been used in disposable industrial garments. Such sheets have been made commercially by E. I. du Pont de Nemours & Co. and sold as "Tyvek" spunbonded olefin. The sheets are known for their good strength, durability, opacity and ability to act as a barrier to particulate matter as small as sub-micron size. Because of these desirable characteristics, the spunbonded sheets have been fashioned into many types of industrial garments, such as those worn by asbestos workers, as disclosed in "Protective Apparel of Du Pont TYVEK.RTM.-SAFETY YOU CAN WEAR", E-02145, (1987). However, the utility of the garments could be greatly enhanced by improvements in the spunbonded sheet from which the garment is made in order to provide a softer and more breathable garment that is more comfortable to the wearer.
Various methods have been suggested for improving spunbonded polyethylene film-fibril sheets as well as spun webs of polyethylene fibers. One of these methods includes water jetting a spun web of fibers to add integrity to the web by entangling and interlocking the fibers in a random manner. This method is well known in the art and is described in Evans, U.S. Pat. No. 3,485,706, the contents of which are incorporated herein. In particular, Example 57 of Evans discloses the preparation of a fabric of high drape and suede-like properties made from a polyethylene nonwoven sheet. The process teaches depositing a three-dimensional network of polyethylene film-fibrils onto a collection belt and then lightly compacting the network by means of pressure rolls to provide a consolidated product having a paper-like hand. The product is then supported on a patterning plate (having 0.048 inch diameter holes in staggered array arranged on 0.08 inch centers) and subjected to high-energy streams of water issuing from a plurality of spaced orifices at between 1500 and 2000 psi. The use of high energy water jets is disclosed in Dworjanyn, U.S. Pat. No. 3,403,862, the contents of which are incorporated herein.
Moreover, U.S. Pat. No. 4,910,075 (Lee et al.) discloses a point-bonded, jet-softened polyethylene film-fibril nonwoven fabric useful as a disposable garment. This fabric is commercially available from E. I. du Pont de Nemours & Co. of Wilmington, Del. under the tradename TYPRO.RTM. PC. The process for preparing the nonwoven fabric comprises passing the sheet through a nip formed by a patterned, heated metal roll and a second, resilient roll to form a repeating boss pattern on the sheet and then subjecting the point-bonded sheet to high energy jets of water supplied from multiple closely-spaced orifices. The garments are comfortable and provide good protection against particulate matter.
However, the nonwoven fabrics described above are only suited for particular applications. These nonwoven fabrics have certain aesthetic and physical deficiencies which need improvement. Specifically, the strength and comfort of these nonwoven fabrics need to be improved so that the fabrics are more acceptable as an article of apparel.
Therefore, what is needed is a nonwoven fabric which provides an adequate degree of barrier and strength while also providing a very high degree of comfort based on heat and moisture vapor transmission. Other objects and advantages of the present invention will become apparent to those skilled in the art upon reference to the attached drawings and to the detailed description of the invention which hereinafter follows.